Details

Autor(en) / Beteiligte

• Akhtar, Parveen
• Dorogi, Márta
• Pawlak, Krzysztof
• Kovács, László
• Bóta, Attila
• Kiss, Teréz
• Garab, Győző
• Lambrev, Petar H.

Titel

Pigment Interactions in Light-harvesting Complex II in Different Molecular Environments

Ist Teil von

• The Journal of biological chemistry, 2015-02, Vol.290 (8), p.4877-4886

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2015

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• Extraction of plant light-harvesting complex II (LHCII) from the native thylakoid membrane or from aggregates by the use of surfactants brings about significant changes in the excitonic circular dichroism (CD) spectrum and fluorescence quantum yield. To elucidate the cause of these changes, e.g. trimer-trimer contacts or surfactant-induced structural perturbations, we compared the CD spectra and fluorescence kinetics of LHCII aggregates, artificial and native LHCII-lipid membranes, and LHCII solubilized in different detergents or trapped in polymer gel. By this means we were able to identify CD spectral changes specific to LHCII-LHCII interactions, at (−)-437 and (+)-484 nm, and changes specific to the interaction with the detergent n-dodecyl-β-maltoside (β-DM) or membrane lipids, at (+)-447 and (−)-494 nm. The latter change is attributed to the conformational change of the LHCII-bound carotenoid neoxanthin, by analyzing the CD spectra of neoxanthin-deficient plant thylakoid membranes. The neoxanthin-specific band at (−)-494 nm was not pronounced in LHCII in detergent-free gels or solubilized in the α isomer of DM but was present when LHCII was reconstituted in membranes composed of phosphatidylcholine or plant thylakoid lipids, indicating that the conformation of neoxanthin is sensitive to the molecular environment. Neither the aggregation-specific CD bands, nor the surfactant-specific bands were positively associated with the onset of fluorescence quenching, which could be triggered without invoking such spectral changes. Significant quenching was not active in reconstituted LHCII proteoliposomes, whereas a high degree of energetic connectivity, depending on the lipid:protein ratio, in these membranes allows for efficient light harvesting. Background: Light-harvesting complex II (LHCII) displays different spectroscopic properties in thylakoid membranes and in detergents. Results: Circular dichroism and fluorescence lifetimes disclose structural effects of protein-protein, lipid-protein, and detergent interactions. Conclusion: The native state of complexes is perturbed by detergents and best retained in lipid:LHCII assemblies. Significance: The lipid environment is important for the proper function of LHCII, the most abundant of membrane proteins.